fletcher

An implementation of Fletcher's algorithm in Rust

Fletcher's Checksum is a checksum algorithm that was developed to provide nearly the same error checking capability as a CRC but with a faster software implementation. This is not a cryptographically secure checksum, it's only meant to be used for checking the integrity of data NOT the authenticity.

Algorithm Pros

This algorithm is faster to run in software than most CRCs. This is because the CRC algorithm was originally designed to be simple to implement in hardware, but not neccesarily in software. The Fletcher Checksum was designed specifically to be suited for implementation in software.

Algorithm Cons

This checksum algorithm does suffer from not being able to distinguish 0xFF from 0x00. Meaning a block of data with all bits set to 1 will have the exact same the same checksum as a block of data with all bits set to 0. This comes from the fact that the algorithm uses one's complement math.

Fletcher's checksum isn't quite as good at detecting bit errors in data as a CRC with a well choosen polynomial.